Lindsey Vonn during the Thursday four ball matches of the Presidents Cup at Muirfield Village Golf Club. / Peter Casey USA TODAY Sports

by Kelly Whiteside, USA TODAY Sports

by Kelly Whiteside, USA TODAY Sports

In ski racing, the fastest path down a steep slope and between and around the gates is called "the line." It's a line between danger and safety. A line Lindsey Vonn has repeatedly crossed throughout her illustrious ski racing career.

"I'm a little bit reckless. It's really rare that I'm afraid to do something. Usually people have to hold me back," Vonn said in an interview with USA TODAY Sports before the season. "I like to do things fast. I drive a car too fast. I jet ski too fast. I'm pretty fearless all around."

Given her nature, there is always reason to hold one's breath when Vonn is wearing Lycra, especially since she's coming back from a serious knee injury. She tore the ACL and MCL in her right knee and fractured her tibia in a brutal crash in Austria on Feb. 5.

Ten days before Vonn was scheduled to compete for the first time since the injury, she crashed in training at Copper Mountain, Colo., on Tuesday morning. She was not admitted to a hospital but was evaluated by her long-time doctor, Bill Sterett, in Vail.

As of Tuesday evening, it wasn't clear whether she re-injured her right knee. Even if the injury doesn't impact her chances of competing at the Sochi Olympics, which begin in 78 days, this will be a white-knuckle ride for Vonn and her support team from now until then.

Maris Van Slyke, 16, was at Copper Mountain to watch the U.S. Ski Team train when she saw Vonn coming off the slope on a sled at 10 a.m. The high school skier from Lake Placid, N.Y., came to the mountain that morning in hopes of getting her picture taken with Vonn. Instead she gained a small measure of Twitter fame by posting a picture of a limping Vonn being helped off the mountain by a few coaches.

U.S. Ski Team spokesman Tom Kelly confirmed to the Associated Press that Vonn was taken off on a sled, which in normal protocol in such cases.

In recent weeks Vonn, 29, who lives in Vail, has said her right knee is 100% and that she had no pain or swelling after her return to the snow. She went to Portillo, Chile, on Aug. 31 to train on skis for the first time since her injury. She eased back into training in close consultation with her doctor and trainer.

The Olympic downhill champion skipped the season-opening giant slalom race in Austria on Oct. 26 because she wanted more time to train. But since her surgery in February, Vonn has been ahead of schedule in her recovery. She originally expected to be back on snow in November.

Vonn's first World Cup was expected to be a downhill race Nov. 29 at Beaver Creek, Colo. The following week the women travel to Lake Louise, Alberta, for a pair of World Cup downhill races and a super-G. Vonn swept all three last season.

She has said this season the Sochi Olympics are her priority. The women's downhill in Sochi is Feb. 12.

"I would love to win as many World Cups as possible but my main focus is definitely on the Olympics," she said before the season. "If I start off slow, it's fine I just want to make sure that by the time I get to Sochi that I'm 100% in those events."

Though it's tough for some to watch the video clip of her gruesome crash from the world championships in February, Vonn said recently that she doesn't even wince when she sees it replayed. Her mother, Lindy Lund, feels otherwise. She said she turns her head.

Sterett, her doctor, says it's even tough for him to watch Vonn race.

"What makes her and most of the girls on the team unique is they're so driven and they have such short memories," Sterett told USA TODAY Sports recently. "If you or I fell the way she fell and then somehow that same year, you were in a starting gate and had to go 70 miles down a hill out there with nothing but Lycra on and a helmet, you'd be a little scared. They have no fear. They don't remember the fall, all they remember is winning."

For Vonn, the combination of going fast, whatever the consequence, and the challenge of trying to improve is what drives her. "Winning is always a great feeling," she said. "But it's mostly about the challenge, putting everything on the line. It's kind of addicting."

Vonn has famously pushed the limits before. Before the start of the women's downhill at the 2006 Torino Olympics, Vonn suffered a serious crash in training, landing hard on her back and left hip. Forty-eight hours after the fall, she was back racing, finishing eighth.

In 2009, she severed a tendon in her thumb and risked future function of it if she was injured again. Four days after surgery, she was back racing.

At the 2010 Vancouver Olympics, Vonn raced despite a severely bruised shin. She won the downhill by more than a half second for the first Olympic medal of her career. She also added bronze in the super-G.

After suffering a concussion, she competed 11 days later at the 2011 world championships, winning a silver medal in the downhill. She later allowed that it was a bad decision, given the run was a bit blurry and she was risking so much.

Heading into Sochi, Vonn said this Olympics would be different because she already has a gold medal. "I feel like the pressure is off," she said two weeks ago. "My childhood dream was to win the Olympics, and I've done that. Everything else is icing on the cake."

The most successful female ski racer in U.S. history, Vonn has four overall World Cup titles and needs just three more World Cup victories to tie Annemarie Moser-Proell's record of 62.

She certainly didn't want what could be a historic season to begin this way. Vonn was with boyfriend Tiger Woods on the sideline at the Denver Broncos game Sunday night.

The next day she tweeted: "Catching some air today in Downhill training." On Tuesday, her training ended in the worst possible way. Being helped off the slope, limping.